The field of microfluidics has advanced to the point that it is fulfilling much of its promise to supplant conventional laboratory fluid handling. The ability to precisely control the movement, accession, allocation, and mixing of minute amounts of fluids and subject those fluids to additional processing, analysis, and the like has helped move the field into the mainstream of scientific research, diagnostics, and medical devices.
As research and diagnostic needs become more and more complex, however, there is a need for the field of microfluidics to similarly advance in complexity, requiring a wide range of new functionalities within the microfluidic context. By way of example, microfluidic systems have been used to deliver and combine reagents within microfluidic channels and then perform subsequent processing and/or analytical operations on those reagents, including, e.g., thermal cycling, separations, optical, chemical or electrical detection, and a host of other operations.
In other applications, microfluidic systems have been used to partition small aliquots of aqueous fluids within flowing streams of immiscible fluids, e.g., oils, in order to compartmentalize reactions within those partitions for separate processing, analysis, etc. Specific implementations of these systems have been used to compartmentalize individual nucleic acids in order to perform quantitative amplification and detection reactions (qPCR).
In another implementation, the GEMCODE™ system from 10× GENOMICS®, discrete droplets in an emulsion contain both template nucleic acids and beads bearing large numbers of oligonucleotide barcodes, where a given bead will have a constant barcode sequence. The barcode is then used to prime replication of fragments of the template molecules within the particular partition. The replicate fragments created within a given droplet will all share the same barcode sequence, allowing replicate fragments from single long template molecules to be attributed to that longer template. Sequencing of the replicate fragments then provides barcode linked-reads that can be later attributed back to an originating long fragment, provide long range sequence context for shorter sequence reads.
Surface wettability of substrates is an important physical property for the design of microfluidic droplet-based assays. Surface wettability can influence droplet generation as well as droplet/emulsion stability. Typically, the surface wettability and emulsion stability is tuned by using surfactants in the dispersed and continuous phases. Surface wettability can also be controlled by coatings and chip materials used. Additionally, the surface roughness/texture also influences emulsion stability especially when the droplets interact with surfaces such as in collection wells of the chips. In particular, roughness induced wetting of surfaces can cause large scale coalescence of emulsion and thereby failed assays.
With increasing demands on microfluidic systems, there is a need to add to the microfluidic tools that can be applied to expand their utility. The present disclosure provides a number of such tools and the uses and applications thereof.